Code responsive control apparatus



Feb. 4, 1941.

c. c. BUCHANAN copE RESPONSIVE CONTROL APPARATUS Filed May 3l, 1940 2Sheets-Sheet 1 Feb. 4, 1941.. Q Q BUCHANAN 2,230,860

CODE RESPONSIVE CONTROL AFPARATUS /\f\Y M M m rm UU vv i uv uv N vvINVENTOR @www HIS TTORNEY Patented Feb. 4, 1941 E UNITED STATES nascePATENT OFFICE CODE RESPONSIVE CONTROL APPARATUS Applicaticn May 31,1940, Serial No.-337,977

13 Claims.y

My-invention relates to code responsive control apparatus; and it hasparticular `reference to code `responsive control apparatusY of theclass employed in railway ftraflic controlling systems utilizing codedenergy of the irequency'code type lor controlling either or bothwaysidesignals and train-carried cab signals.

Railway traic controlling systems of the above described Vclass are-characterizedby the Vfact that suchsystems utilize codeiresponsivecontrol apparatus operated by energy received from a pair of conductors,forselectively; controlling traffic governingdevices inV accordance withthe ratefatwhich en-ergy received from the conductors is` coded; and thecode rateat which such energy is supplied to `the conductors-iscontrolled by traflic conditions in` advance.A Generally speaking, thesupply of energy to `the conductors, which may be the rails oflthertrackway,is periodically` interrupted 'or coded at oneor. another,of a pluralityi of code rates through :the fmedium. of aA code`transmitter or vcoding device; and the code responsive control apparatusestablishes selectivecontrol over its associated trail-lcgoverningdevice i through :the-:medium of decoding apparatus -in cludingcircuits arranged and tuned to be resonantat one or another of the code`rates-at which energy-is supplied from thecode responsiveapparatus toIsuch circuits. beenfound desirable'onthe one :hand to icode orinterruptV thesupply of energy-tothe two'con-` ductors at` relativelylow code rates,- thereby avoidingpitting and undue-wear of the contactstructures incorporated in the code transmitters which other hand it hasbeen found desirable to. supply energy `to thecode responsive apparatuscoded at relativelyfhigh coderatesin order to utilize relatively smalland inexpensive tuningfandl decoding t units for detecting-thevariousrates at which such of the control contacts, andtis subject to failures.

, due tothe breaking vor sticking ofthe mechani- Inf such` systems. ithas i code the supplyof control energy, while on theY cally movingparts. In view of the above-mentionedwand -other importantconsiderations, it is an object of myinvention to provide novel andimprovedcode responsive control apparatus operated by energy ccdedat lowcode rates and incorporating means utilizing no moving mechanical parts4for multiplying or increasing thecode rates at whichsuch apparatussuppliesenergy to its associateddecoding apparatus. A

An additional object ofmy invention isfthe provision of novel andimproved railwayv-trailic` controlling apparatus-ofthe class-operated bycoded energy-ofthe frequency code type.l

A' further objectof my inventionis the provision of novelfand improvedcode responsive control-apparatus of the class adapted'for usein control.systems selectively operated by coded energy` The above-mentioned andother important objects .andcharacteristic fea-tures of my invention20-` which, will become readily apparent from the followingidescription, are-attained in accordance with my invention by providinga controlsystem i employing code responsive apparatus of the saturationtype in Whichthesupply` of energy 2&5.

from' a source-ofalternating current-toan out- A put i winding disposed`on-a'magr1etizable core is controlled inaccordance with the state ofmagnetic flux in such core, and 'the magnetic conditionV of-suchv-coreis controlled `ty4 a, biasing 3Q winding constantly suppliedwithunidirectionalV current `for setting up a given conditionof flux of ione polarity inthe core, and by-a -control winding'supplied with-codedcontrol `energy from apair of'conductors and effective upon such -sup-35T;

plyfor lcreating magnetic ux in the core ofthe oppositerelative polarityandof-such magnitude thatl a resultantiiux of the oppositerelativepolarity is setup finthe core. Inwother words,

I -provide a saturation type code responsive'con- 40 ,i

trol device-wherein the state of flux-in the magnetizablecore-is carriedfrom a given ux condition through a zero or no flux condition to -asubstant-iallyn equivalent flux condition of oppositerelative polarityboth on the supply-of energy to 45..,

the control. winding and when such supply is interrupted, whereby thesupply of current from the output winding ofthe device is caused to becoded at sa.` rate twice the` coderatev at whichV energy is supplied tothe control winding.

I shall describe one form of apparatus embodying myinvention, and shallthen point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is i a diagrammatic Viewillustrating a. preferred form 55 of apparatus embodying my invention.Fig. 2 is a .graphical representation illustrating a typical form ofcontrol energy which may be used in conjunction with the apparatus ofFig. 1. Fig. 3 is a graphical representation which illustrates suchcontrol energy rectified into unidirectional energy, and which alsorepresents the ux created in the core of device SR, shown in Fig. 1, dueto the supply of such rectified energy to control winding I8 of thedevice. Fig. 4 is a graphical representation illustrating the biasing uxnormally present in the core of device SR. Fig. 5 is a curverepresenting the varying resultant flux conditions in the core of deviceSR caused by the inter-V mittent supply of control energy and theconstant supply of biasing energy to such device. Fig. 6 is a curverepresentingthe effective currentsupplied from output winding i6 ofdevice SR in response to the intermittent supply to such device ofcontrol energy of the type representedin Fig. 2.

Referring to Fig. 1, the reference character X designates a stretch ofrailway track over which tra'ic normally moves in the single directionindicated by an arrow in the drawings, and over which traffic movementsare controlled by means of control apparatus embodying my invention andpresently to be described in detail. The protected stretch of track X isprovided with a pair of conductors to which coded energy of thefrequency code type is supplied for controlling traffic governingapparatus in accordance with the rate at which such energy is coded. Asshown, the two conductors comprise the two track rails I and I a of thestretch of track, which rails are divided by means of the usualinsulated rail joints 2, as is the usual practice, into a plurality ofsuccessive adjoining track sections, only one section of which, D--E, isshowny complete vin the drawings.

I Coded control energy is supplied to the rails I and la of section D-Eadjacent exit end E of the section, for selectively controlling suitableapparatus, later to be described, in accordance with the rate at whichVsuch energy is Coded. As shown, the rails I and la are supplied withalternating energy from a suitable source of alternating current such,for example, as a generator not shown but having its opposite terminalsdesignated in the drawings by the reference characters BX and CX. Thisenergy is periodically interrupted or coded at one or another of thecustomary plurality of low code rates utilized in railway signalsystems, by means of a coding device or code'transmitter CT, The deviceCT may take any one of many well-known forms but is illustrated ascomprising a plurality of rotatable cams each 4designated by thereference character K with a distinguishing suflix. The cams K aredriven at `a constant speed of. say, 15 revolutions per minute by amotor M which is constantly supplied with alternating current so thatthe coder is continuously active. Each of the cams K is provided with adifferent number of teeth or projections spaced about its periphery,which teeth successively operate an associated contact member to closeperiodically a circuit controlling contact as the cam is rotated. Forexample, cam Kl is shown provided with twelve; teeth or projections,each of which successively engages a contact member I to closeperiodicallya circuit controlling contact '1 -8. Similarly, cam K2 isshown ,provided with eight teeth, eachengaging an associated contactmemberi9 toclose periodically contact 9-I0; and cam K3 is shown providedwith five teeth each engaging an associated contact member Il to closeperiodically a circuit controlling Contact r lI-l2.

In accordance with certain predetermined conditions, one or another ofthe above-mentioned contact members operated by coder CT is conditionedto interrupt periodically or code the supply of trackway energy to therails of section D-E. As indicated in the drawings, the control of suchtrackway energy may be established by suitable apparatus responsive totraflic conditions on the stretch in advance of vsection D--E. Thedetails of the traffic controlled apparatus controlling the supply oftrackway energy are not shown in the drawings since they form no part ofmy present invention, but such apparatus may comprise the usual decodingrelays, such as relays H, BJ and AJ hereinafter referred to, controlledby traic conditions in advance of section D-E through the medium ofVcode responsive apparatus such as will be hereinafter described, andwhich relays set up or establish one or another of a plurality ofcircuits over which energy is supplied to the primary winding of a tracktransformer TT, which transformer has its secondary winding connected,in series with the usual current limiting impedance 5, across the trackrails l and la adjacent exit end E of section D-E. As is readilyapparent from an inspection of Fig. 1, one of the plurality of circuitsabove mentioned includes contact 1 8 of coder CT and since this contactis operated by each of the twelve teeth of cam Ki of coder CT, energyflowing in such circuit is periodically interrupted or coded at a rateof 180 interruptions per minute. The second of the plurality of circuitsincludes contact 9Ill of' coder CT, which contact is operated by each ofthe eight teeth of cam K2 and hence energy ilowing in this circuit isperiodically interrupted at a rate of 120 times per minute. A third ofthe plurality of circuits lshown includes contact H-IZ of coder CT,which contact is operated by each of the five teeth of cam K3 and as aresult energy flowing in this circuit is periodically interrupted some'75 times per minute.

I have represented graphically in Fig. 2 the form of control energy ofthe frequency code type that is supplied to the rails l and la over atypical one of the abovementioned plurality of circuits. For example,Fig. 2 represents the current flow of the 120 code, in which the onperiods during which energy flows when contact S-Ill of coder CT isclosed are represented by illustrating several successive cycles ofalternating current, while the 01T periods during which no energy flowswhen Contact 9-I0 of coder CT is open are represented by indicating anabsence of such alternating current. It is to be noted that the flow ofenergy in the circuit in which Contact 9-l0 of coder CT is interposed,causes control code of the frequency code type to be supplied to therails of section D-E, which control code is characterized by the factthat the on and off intervals are substantially equal in duration.

Referring to Fig. 1 once more, I have represented the code responsivecontrol apparatus embodying my invention incorporated into a waysidesignaling system for selectively controlling a wayside signal S inaccordance with the rate at which energy supplied to the track rails iscoded. The wayside signal S preferably is located in the trackwayadjacent the entrance end D of section D-E, and may take any one of manywell-known forms, but as shown comprises a four-indication color lighttype signal having a green signal unit G, a yellow over green signalunit Y/G, a yellow signal unit Y and a red signal unit R, which unitswhen illuminated indicate clean approach medium, approach and stop,respectively.

Selective control of the aspects displayed by signal S is effected inaccordance with the rate at which energy supplied to the rails I and I ais coded, by means of code responsive apparatus embodying my inventionand operated by energy derived from the two track rails of section D-E.As shown, such apparatus comprises a novel form of code responsivecontrol device of the saturation type, designated as a whole by thereference character SR; a decoding transformer DT supplied with energyfrom device SR; and the usual code detecting and code selecting relaysI-II, BJ I and AJ I controlled by energy supplied frorn decodingtransformer DT.

The code responsive device SR comprises a magnetizable core I5 uponwhich are disposed an output winding I5, a biasing winding l1 and acontrol winding I8. The biasing winding I'I is constantly supplied withunidirectional current from a suitable source, such for example as arectifier RI which has its output terminals connected to winding I1 andhas its input terminals connected across the secondary winding of atransformer TI. The primary winding of transformer TI is connectedacross a source of alternating current designated by the referencecharacters BX and CX, and it follows that winding I1 is constantlyenergized to create unidirectional :IiuX of a given polarity in core I5to set up a iven flux condition in such core. I have representedgraphically in Fig. 4 the flux condition established in core I5 by theflux due to current in winding I'I, and I shall refer to this biasingflux as being ux of normal polarity and the magnetic condition set up incore I5 by such flux as being the normal flux condition of device SR.

The control winding I8 of device SR is supplied with energy derived fromthe track rails I and Ia for varying the magnetic condition of core I5in step with the supply of such energy. As shown, energy from the railsI and Ia is supplied to winding I8 through the medium of a receivingtransformer RT, which has its primary winding connected across the trackrails of section D-E adjacent the entrance end D and has its secondarywinding connected to the input terminals of a rectifier R2, the outputterminals of this rectifier being connected to winding I8. It is readilyapparent that the alternating energy supplied to the track rails I andIa is rectied by rectier R2 into and is supplied to Winding I8 asunidirectional current. The curve shown in Fig. 3 represents the rectiedcurrent supplied from rectifier R2 to Winding I8 in response to thesupply of 120 code energy to the rails of section D-E, and since suchenergy sets up a unidirectional flux in core I8 proportional to theampere turns of winding I8, such curve also represents the ux created incore I5 due to the supply of such energy to winding I8.

The connection of winding I8 to rectier R2 is selected in such mannerthat the flux created in core I5 due to current in winding I8 opposesthe flux due to current in winding Il. Preferably, the parts of windingIll are selected and designed so that when unidirectional energy of apredetermined magnitude is supplied to winding I8, the normal iiuxcreated by winding I'I is entirely neutralized and a resultant uxcondition is established in the core of substantially equal density andopposite relative polarity to that `of the normal flux condition. Thecurve shown in Fig. 5 represents a typical variation of the magneticcondition of core I5 caused b-y the supplyof biasing flux and of controlflux to such core. In Fig. 5, it is assumed that control flux issupplied to core I5 in responseto the supply to winding I8 of the 120code control energy, such as is represented in Fig. 2.

In Fig. 1, the biasing winding Il and control winding I8 are illustratedcontrolling the magnetic condition of a saturable reactor type coderesponsive device, hence the magnetizable core I5 of device SR isillustrated as comprising, as is the usual practice, a three-leggedstructure having biasing winding II and control winding i8 disposed onthe middle leg of the core and an output winding comprising two coilsIii, I6 disposed one on each of the two outer legs of the core. The twocoils I6, I5 of the output winding are connected together in series to asource of alternating current, and it follows that the impedances of thetWo coils comprising the output winding of device SR are varied in stepwith the variations of the magnetic condition of core I5. Preferably,the connection of the two coils of winding I6 is such that both coilscooperate in circulating a flux in agreement in the two outer legs ofcore I 5, and as a result substantially no alternating ilux traversesthe middle leg of core I5 so that no alternating current components areinduced in windings I'I and I8. It is readily apparent that by properlyproporticning and designing the parts of reactor SR, the magnetizablecore I5 may be normally held at a given uX condition (preferably beingheld at a saturated condition), in response to the'biasing flux createdby winding I1 so that as a result the impedance of winding It isrelatively low and current of relatively high magnitude flows throughwinding I 5. When, however', control energy is supplied to winding I3,the flux due to current ini winding I8 flrst carries the core through anunmagnetized or no-ilux condition, wherein the impedance of winding itisgreatly increased and the current flow in such winding is decreased to arelatively low Value, to a resultant flux condition of substantiallyequivalent or saturated density of iluX of opposite relative polarity,wherein the current ilow in winding I5 again reaches its normally highvalue. On the interruption of current to winding I8, a similar variationin ilux condition of the core is established with a` correspondingvariation in magnitude of current traversing winding IS. The curveillustrated in Fig. 6 represents the effective current flo-w in windingI5 of device SR under the conditions wherein code is supplied to controlwinding I5 of the device. It is to be noted from Fig. 6 that the numberof code impulses supplied from output winding I6 of device SR per unitof time is double the number of code impulses supplied to winding I8 inthe same interval of time (see Fig. 3), hence it follows that device SRfunctions to increase the code rate or frequency at which energy issupplied to' its associated decoding apparatus in response to the supplyof coded control energy to device SR.

It should be pointed out that by means of biasing winding Il, energysupplied through winding I under the'influence of coded current inwinding I8 is caused to be coded at a'rate double the code rate ofenergy supplied to Winding I8, whereas if biasing Winding I1 is notemployed, the coding of current in Winding I6 caused by the supply ofcoded current to winding I8 results merely in reproducing in winding l5the coding of the current in winding I8. Ihis follows from the fact thatif only winding I8 were employed, the reluctance of core I5 then wouldvary from a relatively high value to a relatively low value in step withthe supply of current to winding i8 and current in winding I6accordingly would vary in step with the supply of the coded impulses ofcurrent in winding I8. The effective current in winding I6 under suchassumed conditions would, therefore, be represented by a curvesubstantially similar to that shown in Fig. 2. When, however, biasingwinding I'I is employed to set up an initial or normal ux in core I5,the supply of current to winding I8 then causes the reluctance of coreI5 to vary from a relatively high value to a relatively low value twicefor each impulse of code supplied to winding I8, and as a resultcurrentl in winding I6 is caused to be coded at a rate double the rateat which current supplied to winding I8 is coded.

As shown in Fig. l, output winding I6 of device SR supplies energy to aportion of the primary winding of a decoding transformer DT through themedium of a transformer T2 and a rectifier R3, which rectifier isconnected to cause energy supplied from winding I6 to create in itsassociated portion of the decoding transformer a ux which opposes the uxnormally created in the remainder of the primary winding by energysupplied from a rectier R4 constantly connected through a transformer T3to a source of alternating current. Preferably, the parts of decodingtransformer DT are so designed and proportioned that a predetermineddensity of magnetic flux of one polarity is set up in the core oftransformer DT by the constant supply of energy from rectifier R4, andsuch magnetic flux is entirely neutralized and a resultant magnetic uxof substantially equal density but of opposite relative polarity iscreated in the core of transformer DT on the supply of energy fromdevice SR. It can be seen, therefore, that the magnetic condition oftransformer DT is carried from a given flux condition through its vzeroor no flux condition to a substantially equivalent ux condition ofopposite relative polarity both on the supply and on the interruption ofenergy from device SR so that an electromotive force is induced in thesecondary winding of transformer DT due to the variations in flux in thetransformer core.

The secondary Winding of transformer DT is connected to supply energy tosuitable decoding apparatus, whichapparatus includes the usual decodingrelays one for each of the plurality of code rates supplied to the railsof the trackway, whereby selective control of trafc governing signal Sis established in accordance with the rate at which control energy issupplied to device SR. As shown, signal S is controlled to one oranother of a plurality of distinctive signal aspects through the mediumof three decoding relays AJ I, BJI and HI one foreach of the threeassumed rates of coding, and which relays are coupled with the secondarywinding of transformer DT through the medium of suitable decoding orcode distinguishing units DUI, DU2 and DUS, respectively.

The details of construction of the decoding units DUI, DU2 and DU3 arenot shown in the drawings, but such units usually comprise a rectifierand a reactor condenser tuning unit tuned to resonance respectively at afrequency correspending to a predetermined multiple of the 180, 120 and75 code rates supplied to the track rails, whereby relays AJ I, BJI andIII are effectively energized and picked up when and only when thepredetermined multiple of its associated control code, at least, issupplied from decoding transformer DT to such relay. That is to say, theconstruction and design of the decoding units DU preferably are suchthat relay HI is energized by current supplied through decoding unit DU3when transformer DT supplies the predetermined multiple of the r15 code;relay BJ I is energized by current supplied through decoding unit DU2when transformer DT supplies the predetermined multiple of the 120 code;and relay AJ I is energized by current supplied through decoding unitDUI when and only when transformer DT supplies the predeterminedmultiple of the 180 code to such relay.

The operation of the apparatus of Fig. l is as follows: the rails ofsection D-E are supplied With control energy of 180, 120 or '75 code inaccordance With traflic conditions in advance of the section, and whensection D-E is unoccupied, this control energy is supplied from therails of section D--E to device SR. The parts of the apparatus whichsupply control energy to and which receive control energy from the trackrails are designed and proportioned so that under the most unfavorableballast conditions expected to be met in practice, energy of apredetermined magnitude is supplied to device SR sufcient, at least, tocreate in core I5 of device SR a resultant flux condition substantiallyequivalent in magnitude and opposite in relative polarity to the givennormal flux condition established in the core of device SR due tocurrent constantly supplied to biasing winding I1.

If the rails of section D-E are supplied with 180 code and the sectionis unoccupied, then device SR functions in response to energy receivedby winding I 8 from section D-E to supply energy of double the rate or360 code to transformer DT. This supply of energy of double rate or 360code to transformer DT causes induced electromotive forces to besupplied from the secondary winding of the transformer and as a resultrelay AJ I is energized and signal S is caused to display its clearaspect over a circuit extending from one terminal B of a suitable sourceof current, such as a battery not shown, through front contact 2| ofrelay AJ I and the filament of signal unit G of signal S to the otherterminal C of the source of current. Under the assumed conditions ofcode in the trackway, it is immaterial Whether or not relays BJ I and HIare also picked up since at this time these latter relays do not exert acontrol over signal S, but if the decoding unitsY DU are high-passfilters, relays BJ I and HI also will be picked up, as shown in Fig. 1,in response to the current that is supplied from transformer DT.

If, now, 120 code is supplied to the rails I and la. and it is receivedby the code responsive device SR, such device functions to supply energyof double code rate or 240 code to transformer DT, which transformer inturn supplies the current caused to be induced in its secondary wind- 1ing to the relaysAJ I ,LBJ I ,andfI-II. ;By virtue oi r winding iscontrolled'by varying the relative rethe construction and .arrangementofpthe .decoding unitsDU, relay .AJ I is releasedbut relay BJI visApicked up in.. response to the, current vcaused. to be suppliedfromrtransformenDTunder the assumed conditionsof..120 codelirithe trackrails, so that as-a result signal. S controlled to display its vapproachmedium! aspect over a circuit extending from terminal B through backcontact 22 of relay AJ I, front contact 230i relay BJI and the lamentsof `signal unit Y/G of signal S to terminal uC`.

l In the event that-75 codeeissupplied to the 1 rails of sectionvD---Iilv and is received `by device SR, then suchdevice functions to*supply` energy of-a double rate or 150 code to transformer DT,

*f and such transformer supplies; relays-HI, AJ land BJI withthe-currentcaused to beY induced in transformer DTdueto vthersupply of`150 code. vAs` pointed out heretofore, the' decoding units DU functionin such` manner that only relay I-II is picked up in response to thesupply of the predetermined multiple of 75 code; and as a result signalS is controlled to its approachaspect over a circuit `which passes*from" terminal B through back contact 22 of relay AJ I, back contact 24of relay BJ I,"` front contact" 25 'of relay HI and the filament of unitY of signal S to i terminal C.

` If, however, section D`E is occupiedso that the control energysupplied .to its rails is shuntd away from device'SR, then the impedanceof winding I6 of such device is constantly held at a low value by thebiasing flux present in core I5,

. circuit extending from terminal B through back contact 22 of relay AJI, back Contact 24 of relay BJI, back contact 26 of relay HI and thelament of unit R. of signal S to terminal C.

From the foregoing description of the operation of the apparatus of Fig.1, it is readily apparent that I have provided novel and improvedcontrol apparatus of the statictype involving no moving parts andresponsive to control code for proportionately increasing or multiplyingAthe `code rate at which energy is supplied to control .Y apparatusfromthe device in response to. the Vsupply of coded energy to such` device.

It is to be understood, of course, thatthe -particular construction ofthe code responsive saturation device SR shown in Fig. 1 is merelyillustrative, and that such device may takerother `65V suitable formswherein the supply of energy from an output winding is vcontrolled byamagnetizable core in which the flux in a'portion, at least, of suchcore varies between a given iiux condition and a substantiallyequivalentresultant flux condition of opposite relative polarity both on `thesupply and on the interruption of `control energy to such device. Forexample, the code responsive device may take the form of a saturabletransformer wherein the inductive coulffplingbetween a primary windingconstantlysupplied -with alternating current andan output luctances orflux conditions of different portions ofa magnetizable core whichcarriessuch primary. and output windings.

In addition, it is to be understood that although the apparatusembodying my invention zhas been illustrated anddescribed as applied tothe cori-trol of a wayside signal, such apparatus may if desired becarried on a train to control a train-carried control device in responseto controlenergy inductively received from the rails of .a `trackway.

Although I have hereinshown andA described 1 only one form of coderesponsive control ap-V another of a plurality of code ratesin`accordance'.

with Vcertainpredetermined conditions, a magnetizable core having meansfor establishing in said core a normal liux condition of given densityand relative polarity, a control winding disposed on said core, meansfor supplying from said con-- ductors` to said controllwinding energyofa predetermined magnitude and polarity for establishing insaidcore aresultant iiux condition substantially equivalent in density and.oppositen relative polarity-to said .given flux condition, an;v

output winding disposed onisaid core, and a source ofalternatingrcurrent coupled through` said output windingtodecodingapparatus selectively responsive to the rate at which energy isAsupplied thereto.

2. In combination with a source of. current having means forperiodically interrupting or coding such current at one or another of aplurality of code rates, Atwo magnetizable cores each having means forestablishing in its respective core a normal flux condition of givendensity and relative polarity, twocontrol windings one: disposed oneachecore, means for supplying from said source to anrst of said`control windings current `of` a; magnitude l and polarity selected toAestablish in'its associated first core a .resultant flux conditionsubstantially equivalent in density `and. opposite in relativepolaritytosaid normal iiuxcondition, an output winding disposed on saidrst core and connected to the other of saidi two control windings forsupplying to said other control winding current of a predeterminedmagnitude and polarity effective to establish in the `other ofsaid twocores a resultant flux substantially equivalent in density and oppositein rel-"' ative polarity to-said normalxiiux condition, another outputwindingdisposed on said other core, and control means receiving energyfrom. said Aother output winding and selectively -responsive to the formof lenergy supplied thereto.

3. In combination with a sourceof current having means for 4periodicallyinterrupting or coding such-current at one -or anotherl of a` pluralityof code rates, two magnetizablecores each having means -for festablishing l in its respective' core anormal-linx condition of givendensity and relativepolarity,` two contro-1 windings one disposed oneach core, means for supplying from said source to a rst of said controlwindingsunidirectional current of a magnitudeand `polarity 'v selectedto establish in its associated Yfirst core a l resultant flux conditionsubstantially equivalent "winding for establishing in its associatedother core aresultant iiux substantially equivalent in density andopposite in relative polarity to said normal flux condition, anotheroutput winding disposed onsaid other core, and control appara- -Y tusconnected to receive current induced in said other output winding andselectively responsive l to the rate at which such current is varied.

. 4. In .combination with a pair of conducto-rs supplied at times withenergy coded at one or another of a plurality of code rates inaccordance with certain predetermined conditions, a magnetizable core,means for supplying magnetic ux of `a given polarity to said core fornormally estab'- trol winding disposed on said core and proporlishing agiven flux condition in said core, a contioned in such manner that whensupplied with unidirectional energy of a predetermined magnitude andpolarity said winding supplies flux of the .opposite relative polarityto said core for establishing in said core a resultant flux conditionopposite in relative polarity but substantially equivalent in density tosaid given flux condition, means for supplying said control winding withenergy of said predetermined magnitude and polarity derived from saidpair of conductors for energizing said control winding in step withthesupply of energy to said conductors, an output winding disposed onsaid core and receiving energy from a source of alternating currentunder the influence of the magnetic flux in said core,

and control apparatus controlled by energy supplied from said outputwinding and selectively responsive to the rate at which such energy iscoded.

5. In combination with a stretch of railway track having two conductorsgoverned by traffic conditions on said stretch and having means forsupplying to said conductors energy which is coded at one or another ofa plurality of code 'rates in accordance with trafiic conditions inadvance, a magnetizable core, means for supplying to said core magneticflux of a given polarity for normally establishing a given fluxcondition in said core, a control winding disposed on said core andproportioned in such manner that when supplied with unidirectionalcurrent of a predetermined magnitude and polarity said winding Suppliesflux of the opposite relative polarity to said core for creating in saidcore a resultant flux condition opposite in relative polarity butsubstantially equivalent in density to said given flux condition, meansfor supplying said control winding with unidirectional current of saidpredetermined magnitude derived from said two conductors for energizingsaid control winding in step with the supply of energy to saidconductors, an output winding disposed on said core and receiving energyfrom a source of alternating current under the influence of the magneticflux in said core, and railway traiiic controlling apparatus selectivelycontrolled by energy supplied from said output winding in accordancewith the rate at which such energy is coded for governing traffic onsaid stretch.

'6.4 In combination with ai stretch of railway track having means forsupplying coded trackway energy to the rails of said stretch, amagnetizable core normally, held at an initially saturated conditionby'flux of a given polarity, a control winding disposed on said core,means for supplying unidirectional energy of a predetertrack havingmeans for supplying coded trackway energy to the rails of said stretch,a magnetizable core normally held at an initially saturated'condition byflux of a given polarity, a control winding disposed on said core, meansfor supplying unidirectional energy of a predetermined magnitude andpolarity from the rails of said stretch to said control winding forsaturating said 'core withresultant flux of the opposite relativepolarity, a source of alternating' current, railway traic controllingapparatus for controlling traffic on said stretch and selectivelyresponsive to the code rate at which current is supplied thereto, and anoutput winding disposed on said core for coupling said source to saidcontrol apparatus whereby such apparatus is supplied with coded currentfrom said source in response to the iiux conditions in said core.

8. In combination with a stretch of railway track having means forsupplying to the track rails of said stretch trackway energy which iscoded at one or another of a plurality of different rates of coding, amagnetizable core provided with means for supplying ux oi a givenpolarity to said coreV for establishing a flux condition of givendensity in said core, a control winding disposed on said core andproportioned in such 'manner that when supplied with unidirectionalenergy of a predetermined polarity and magnitude said winding sup-pliesto said core ux of the opposite relative polarity and of such magnitudethat a resultant flux condition substantially equal in density andopposite in relative polarity to said given flux condition is created insaid core, means responsive to said trackway energy for supplying tosaid control winding unidirectional;

energy of said predetermined polarity andmagnitude, an output windingalso disposed on said core, and railway traffic controlling apparatuscontrolled by energy supplied from said output winding and selectivelyresponsive to the codingof such energy as effected by the varying uxconditions in said core.'

9'. In combination with a stretch of railway track having means forsupplying to the track rails of said stretch trackway energy which iscoded at one or another of a plurality of different rates of coding, amagnetizable core provided with means for supplying flux of a givenpolarity to said core for establishing a given flux condition in saidcore, a control winding disposed'on said core, means responsive to saidtrackwayenergy for supplying to said control winding unidirec- .tionalenergy of a predetermined polarity and magnitude for creating in saidcore a resultant flux condition substantially equivalent in density andopposite in relative polarity to said given flux condition, an outputwinding also disposed on said core, a source of alternating current,decoding means supplied with energy from said source through said outputwinding andselectively responsive to variations in such energy aseffected in response to varying impedance conditions of said outputwinding caused by varying flux conditions in said core, and railwaytraic controlling apparatus selectively controlled by said decodingmeans for controlling traffic in said stretch.

l0. In a code control system of th-e class wherein coded' currentsupplied from a control circuit selectively controls code responsivecontrol apparatus in accordance with the rate at which such current iscoded, the combination with said circuit and said control apparatus of acode repeating device receiving from said circuit current coded at oneor another of a plurality of code rates and supplying current to saidcontrol apparatus at an increased rate of coding proportional to therate at which the received current is coded, said device comprising asource of alternating current and a magnetizable core carrying an outputwinding coupled With said source and supplying current to saidcontrol-apparatus, said core also having means for varying the flux insaid core between ilux conditions of substantially equivalent densitiesand of opposite relative polarities both on the supply and on theinterruption of current to the device from said circuit, whereby thesupply of current from said source to said control apparatus throughsaid output Winding is caused to be coded at a rate double the rate atwhich current is received by the device from said source.

11. In combination with decoding apparatus adapted to be selectivelycontrolled in accordance with the rate of coding at which current issupplied from a control circuit, a magnetizable core,

a source of alternating current coupled with an output winding disposedon said cor-e for supplying current to said decoding apparatus, andmeans on said core responsive to current supplied frorn said controlcircuit for varying the magnetic flux in said core between fluxconditions of substantially equivalent densities and of oppositerelative polarities both on the supply and on the interruption ofcurrent from said control circuit.

12. In combination with decoding apparatus adapted to be selectivelycontrolled in accordance with the rate of coding at which current issupplied from a control circuit, a magnetizable core, means on said coreresponsive to current supplied from said control circuit for varying themagnetic iiux in said core between flux conditions of substantiallyequivalent densities and of opposite relative polarities both on theSupply and on the interruption of current from said control circuit, anda source of periodically varying current connected through an impedancewinding disposed on said core to said decoding apparatus.

13. In combination With decoding apparatus f adapted to be selectivelycontrolled in accordance with the rate of coding at which current issupplied from a control circuit, a magnetizable core, means on said coreresponsive to current supplied from said control circuit for varying themagnetic ux in said core between ilux conditions of substantiallyequivalent densities and of op posite relative polarities both on thesupply and on the interruption of current from said control circuit, anda source of alternating current coupled through a winding disposed onsaid core to said decoding apparatus for supplying such apparatusy withcurrent caused to be coded in response to variations of flux in saidcore.

CHARLES C. BUCHANAN.

